1. Field of the Invention
The invention relates in an aspect to a method for producing a polyether ether ketone.
2. Description of Related Art
Polyether ether ketone (PEEK) belongs to the group of the polyaryl ether ketones (PAEK). These high performance plastics are employed in ever increasing quantity in the areas of automobiles and rolling stock, aerospace, mechanical and apparatus engineering, electrical engineering and cables, electronics and semiconductors, medical technology as well as the food processing industry.
PEEK has the subsequently illustrated general structural formula (III):

According to a method known from prior art the production of PEEK takes place by a Williamson ether synthesis based on 4,4′-difluorobenzophenone and hydroxyquinone which is first deprotonated with sodium carbonate. The polycondensation here typically takes place at 300° C. in the high-boiling solvent diphenyl sulfone (Ph2SO2). This reaction scheme is represented subsequently:

The high reaction temperature can be explained by the low solubility of PEEK in standard solvents at room temperature. The high reaction temperature, however, entails numerous drawbacks:                Due to the entropy effect the polymer yield and the molecular weight are lower than at lower temperatures.        At high temperatures uncontrollable side reactions occur. One problem here is that hydroxyquinone can easily be oxidized into quinone. Both compounds form a colored charge-transfer complex which negatively affects the color of the usually white PEEK.        Using the costly fluoride-containing starting product 4,4′-difluorobenzophenone as well as the likewise costly solvent diphenyl sulfone is imperative.        